1. Field of the Invention
The present invention relates to a navigation device and a control method thereof; and more particularly to a navigation device and a control method thereof that are able to determine a manner of displaying a road map based on a driving speed.
2. Description of the Related Art
In the past, Global Positioning System (GPS) is mainly used in airplane/ship navigation or geographical surveying. However, the application of GPS system has now gradually extended into people's daily life. For example, GPS system has replaced the old radio beacon used in aerial navigation, or is used along with electronic maps for car navigation to enable a driver to easily locate desired road signs, or is used to locate someone's current position, or is used along with a satellite locator by skiers, hikers, nature-lovers and climbers to locate destination and the shortest route to home. Therefore, it has become an important trend in technological fields to develop GPS system with more functions. Currently, GPS system is most widely developed and applied in car navigation.
In displaying roads surrounding the driver (i.e. the user), the conventional car navigation systems tend to display all the surrounding roads in the display screen. However, the user is not able to determine which road information is useful to him or her and which navigation message is meaningless to him or her. Thus, the user tends to take time to watch the display screen for reading and determining the displayed messages and becomes distracted from driving to easily result in an accident.
U.S. Pat. No. 6,049,755 discloses a method for displaying current vehicle location using a navigation system, in which the navigation system determines whether to display cross streets based on the importance of the cross streets. When the user's car is moving on a road that has an importance higher than a threshold value, the navigation system would determine not to display cross streets that have importance lower than the threshold value. However, up to date, no one has suggested the technique of adjusting the information displayed on the navigation device according to the driving speed. Therefore, it is possible a user driving at a high speed is distracted from driving when trying to watch the complicate information displayed on the navigation device, and is therefore subject to the danger of an accident.